1. Field of Invention
Fixed prosthetics (crown and bridge) modeling requires the molding of cast tooth die sections, typically each with 1-3 teeth on a cast model with a base support. The body of the dental dowel pin fits into a slot in the base formed by insertion of the dowel pin into the base while the mix is in liquid form. Thus the base forms the negative impression of the pin. The head part of the dental dowel pin, which is typically a small cylindrical knurled or grooved rod, is held fast in the die section itself.
A typical ordinary dowel pin is made of tapered brass, the smaller end of which fits into a retaining slot. It may have one or two flat sides to prevent rotation when fully engaged in the base, but as a result of its taper, such a dowel pin sacrifices retention ability at the base of the pin and furthermore dust or wear will soon limit the accuracy of alignment possible with the model with which the pin is used.
In the case of the present invention, the geometry of the dowel pin is specially shaped to eliminate the taper, and the sides of the dowel pin all meet the endplane of the pin at 90.degree. degrees. The centerlines of two inverse angle indentations on opposite sides of the pin also meet the end plane at 90 degrees. The walls of each of these indentations, also at 90 degrees to the end plane, further increase the amount of conjoined walls to assure accurate replacement of the pin no matter how often it is removed and replaced in the course of the dental modeling for which the aforesaid cast are designed to be utilized.
2. Description of the Prior Art
Many existing dowel pin systems utilize a plurality of pins to achieve the desired placement and alignment functions, and otherwise make the processing inconvenient and time consuming. Alternatively, many other dowel pin systems have used sleeves embedded in the base cast that are normally formed by inverting the projecting ends of the dowel pin into the sleeves prior to pouring the base cast material and then letting the material harden around the sleeves. Such sleeves are found to rotate or otherwise lose their alignment upon use. The greater simplicity, stability, accuracy, and ease of utilization of the dental dowel pin of the present invention are advantageous for its utilization in the dental laboratory.
Prior art generally illustrating the field of the invention includes the following U.S. patents:
______________________________________ Inventor U.S. Pat. No. ______________________________________ H. Blitz 4,443,192 H. Imaizumi 4,371,340 M. der Avanessian 4,363,625 W. B. Dragan 4,139,943 F. M. Kulig, et al. 3,969,820 R. E. Huffman 3,937,773 B. Weissman 3,875,665 P. Eberhard 3,798,772 ______________________________________
The Blitz patent (U.S. Pat. No. 4,443,192) discloses a tapered dowel pin with a head portion characterized by a plurality of tooth-engaging barbs. Imaizumi (U.S. Pat. No. 4,371,340) discloses a hard plastic denture model pin of frustoconical geometry with one or two flat sides. Der Avanessian (U.S. Pat. No. 4,363,625) discloses a tapered tool retainer pin of cusped transverse cross section fitting into a cooperative seat mounted in the model base support. Dragon (U.S. Pat. No. 4,139,943) discloses a double pronged pin interconnected by a bridge and a method for making a dental die using the pronged pin. Kulip, et al., (U.S. Pat. No. 3,969,820) discloses a tapered composite dowel pin made of synthetic resin with a planar surface and diametrically opposed rib.
Huffman (U.S. Pat. No. 3,937,773) discloses a dental model with a plurality of parallel nontapered guide pins slidably seated within cylindrical cavities in an apertured retainer. Weissman (U.S. Pat. No. 3,875,665) discloses a tapered pin of elliptical transverse cross section, a mounting post extended in the opposite parallel direction, and a short key structure projected radially from the region of the mounting post. Eberhard (U.S. Pat. No. 3,798,772) discloses a tapered dowel pin that passes through a central plate with an orienting noncircular pedestal forming a socket for the pin. The above prior art examples lack the vertically sided and indented geometry of the present dental dowel pin which offers an increased amount of conjoined area between the pin and its retaining slot.